$shadow-key-umbra-opacity = rgba(0,0,0, .2)
$shadow-key-penumbra-opacity = rgba(0,0,0, .14)
$shadow-key-ambient-opacity = rgba(0,0,0, .12)

$shadow-key-umbra = 0px 0px 0px 0px $shadow-key-umbra-opacity,
                    0px 2px 1px -1px $shadow-key-umbra-opacity,
                    0px 3px 1px -2px $shadow-key-umbra-opacity,
                    0px 3px 3px -2px $shadow-key-umbra-opacity,
                    0px 2px 4px -1px $shadow-key-umbra-opacity,
                    0px 3px 5px -1px $shadow-key-umbra-opacity,
                    0px 3px 5px -1px $shadow-key-umbra-opacity,
                    0px 4px 5px -2px $shadow-key-umbra-opacity,
                    0px 5px 5px -3px $shadow-key-umbra-opacity,
                    0px 5px 6px -3px $shadow-key-umbra-opacity,
                    0px 6px 6px -3px $shadow-key-umbra-opacity,
                    0px 6px 7px -4px $shadow-key-umbra-opacity,
                    0px 7px 8px -4px $shadow-key-umbra-opacity,
                    0px 7px 8px -4px $shadow-key-umbra-opacity,
                    0px 7px 9px -4px $shadow-key-umbra-opacity,
                    0px 8px 9px -5px $shadow-key-umbra-opacity,
                    0px 8px 10px -5px $shadow-key-umbra-opacity,
                    0px 8px 11px -5px $shadow-key-umbra-opacity,
                    0px 9px 11px -5px $shadow-key-umbra-opacity,
                    0px 9px 12px -6px $shadow-key-umbra-opacity,
                    0px 10px 13px -6px $shadow-key-umbra-opacity,
                    0px 10px 13px -6px $shadow-key-umbra-opacity,
                    0px 10px 14px -6px $shadow-key-umbra-opacity,
                    0px 11px 14px -7px $shadow-key-umbra-opacity,
                    0px 11px 15px -7px $shadow-key-umbra-opacity

$shadow-key-penumbra = 0px 0px 0px 0px $shadow-key-penumbra-opacity,
                        0px 1px 1px 0px $shadow-key-penumbra-opacity,
                        0px 2px 2px 0px $shadow-key-penumbra-opacity,
                        0px 3px 4px 0px $shadow-key-penumbra-opacity,
                        0px 4px 5px 0px $shadow-key-penumbra-opacity,
                        0px 5px 8px 0px $shadow-key-penumbra-opacity,
                        0px 6px 10px 0px $shadow-key-penumbra-opacity,
                        0px 7px 10px 1px $shadow-key-penumbra-opacity,
                        0px 8px 10px 1px $shadow-key-penumbra-opacity,
                        0px 9px 12px 1px $shadow-key-penumbra-opacity,
                        0px 10px 14px 1px $shadow-key-penumbra-opacity,
                        0px 11px 15px 1px $shadow-key-penumbra-opacity,
                        0px 12px 17px 2px $shadow-key-penumbra-opacity,
                        0px 13px 19px 2px $shadow-key-penumbra-opacity,
                        0px 14px 21px 2px $shadow-key-penumbra-opacity,
                        0px 15px 22px 2px $shadow-key-penumbra-opacity,
                        0px 16px 24px 2px $shadow-key-penumbra-opacity,
                        0px 17px 26px 2px $shadow-key-penumbra-opacity,
                        0px 18px 28px 2px $shadow-key-penumbra-opacity,
                        0px 19px 29px 2px $shadow-key-penumbra-opacity,
                        0px 20px 31px 3px $shadow-key-penumbra-opacity,
                        0px 21px 33px 3px $shadow-key-penumbra-opacity,
                        0px 22px 35px 3px $shadow-key-penumbra-opacity,
                        0px 23px 36px 3px $shadow-key-penumbra-opacity,
                        0px 24px 38px 3px $shadow-key-penumbra-opacity

$shadow-key-ambient = 0px 0px 0px 0px $shadow-key-ambient-opacity,
                      0px 1px 3px 0px $shadow-key-ambient-opacity,
                      0px 1px 5px 0px $shadow-key-ambient-opacity,
                      0px 1px 8px 0px $shadow-key-ambient-opacity,
                      0px 1px 10px 0px $shadow-key-ambient-opacity,
                      0px 1px 14px 0px $shadow-key-ambient-opacity,
                      0px 1px 18px 0px $shadow-key-ambient-opacity,
                      0px 2px 16px 1px $shadow-key-ambient-opacity,
                      0px 3px 14px 2px $shadow-key-ambient-opacity,
                      0px 3px 16px 2px $shadow-key-ambient-opacity,
                      0px 4px 18px 3px $shadow-key-ambient-opacity,
                      0px 4px 20px 3px $shadow-key-ambient-opacity,
                      0px 5px 22px 4px $shadow-key-ambient-opacity,
                      0px 5px 24px 4px $shadow-key-ambient-opacity,
                      0px 5px 26px 4px $shadow-key-ambient-opacity,
                      0px 6px 28px 5px $shadow-key-ambient-opacity,
                      0px 6px 30px 5px $shadow-key-ambient-opacity,
                      0px 6px 32px 5px $shadow-key-ambient-opacity,
                      0px 7px 34px 6px $shadow-key-ambient-opacity,
                      0px 7px 36px 6px $shadow-key-ambient-opacity,
                      0px 8px 38px 7px $shadow-key-ambient-opacity,
                      0px 8px 40px 7px $shadow-key-ambient-opacity,
                      0px 8px 42px 7px $shadow-key-ambient-opacity,
                      0px 9px 44px 8px $shadow-key-ambient-opacity,
                      0px 9px 46px 8px $shadow-key-ambient-opacity

// MIXINS
elevation($z, important = false)
  box-shadow: $shadow-key-umbra[$z],
              $shadow-key-penumbra[$z],
              $shadow-key-ambient[$z] (important ? !important : )

elevationTransition($duration = 280ms, $easing = cubic-bezier(.4, 0, .2, 1))
  transition: box-shadow $duration $easing
  will-change: box-shadow
